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Offline Homefire
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« Reply #10 on: October 24, 2010, 03:07:05 pm »
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Because of all the Level adjustments I have to Calibrate mine prior to any use with a known level.

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« Reply #11 on: October 24, 2010, 03:27:04 pm »
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Hi levettp
         you can Calibrate  by using small soft name frequency counter 1.01         download it and test an signal you know the valuo and read the resault.
         
best time
j.

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« Reply #12 on: October 24, 2010, 04:36:09 pm »
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Hi levettp

I have a simple schematic to make a probe but I cant seem to find it at the moment but like GD was telling you place a 10M resistor for the moment. If your square wave becomes a sine wave then disappears it's your oscillator that simply not continuing to oscillate the sound card scope got nothing to do with it.

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Offline levettpTopic starter
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« Reply #13 on: October 25, 2010, 01:44:05 am »
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Thanks Xavier

I did find some probe schematics but would like to see what you are using.

I generate my test pulse with a PIC processor so it is stable.

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Levett

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Offline xavier
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« Reply #14 on: October 25, 2010, 05:28:45 am »
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Hi levettp

I have never had any problem with Zelscope if your wave form becomes a straight line it's your oscillator that is not oscillating not the program. I don't know what experience you have in PIC programing but I for one don't have any so I cant help you there. I suggest that you build an oscillator using an NE555 use an LED as an indicator that it's running then try you PC scope.

Regards Xavier     

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« Last Edit: October 25, 2010, 06:08:47 am by xavier »
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« Reply #15 on: November 05, 2010, 12:26:50 am »
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Morning Zavier

I still can't get this thing to work. Am going to try it on a Windows XP PC to see if it helps.

I'm quite competent with the PIC I'm using so the problem is definately not with the input signal.

Regards

Levett

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Offline xavier
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« Reply #16 on: November 05, 2010, 01:46:33 am »
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Strangely I have no problem with it. Did you try to make an oscillator like I told you? 

Regards Xavier

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« Reply #17 on: March 25, 2011, 04:53:08 pm »
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Use of digital processing allows considerably to simplify an electronic part of the detector. But to keep thus main units. It is a power unit, generator of pulses, preliminary amplifier and two (one) coils.
For example for the project 22 it is possible to remove microcircuits IC7, IC8, IC9, I1C1, IC12 and components for them.

The presence of metal is defined(determined) on change of the integated summ l for the chosen period of time . There is no necessity to move by the search coil to the left to the right. At a finding of the coil above metal object the sum of integration at once is increased.
At 16 bit of sound card it is possible to catch even insignificant changes of this sum, that considerably increases sensitivity of the detector. The senstivity theoretically will be equal 1/16384. Actually it it is a little less, but substantial growth of sensitivity in comparison with existing types of detectors. (Pulse induction MDUsing regression analyses for digital processing of a signal allows to discrimanate of the metals.
But it is necessary to know that resolution of the digital detector much more depends on a used sound card (if at processing a signal the sound card is used). The resolution on time depends on sample rates. And on amplitude from number bits (8, 16, 24 bits).
The program made mine, is oriented on a card with 8/60 bits and sample rates (11025 to 48000 sps). It is possible to be switched to 8 bits at frequency 96000. But then the resoulution on amplitude (1/256) decreases.. Time resolution is 10 micro seconds (iti is considerably increased)
The variant of my program of the pulse analyzer is placed below. And you can free downlload . But it is necessary to remember that the level of input signal (after the preliminary amplifier of the detector) must be less 0,5 volts. In mentioned variant of program is adjusted on a sound card Realtek AC97. If You to use other card that it is necessary to make changes to the program.


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« Reply #18 on: March 26, 2011, 05:12:05 am »
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Hi Wus47

I?m going to download your programme I don't have a Realtek sound card so I don't know how it will work but I am eager to see what you have done. It also sounds like you have quite a bit of knowledge regarding programming and metal detectors have you build your own using PIC's?  or are you suggesting that these components can be replaced by a PIC?

All the best
Xavier


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« Reply #19 on: March 26, 2011, 09:43:00 am »
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Hi Xavier!
Excuse me for my bad English. My native is the Ukrainian. On a  Geotech forum I have created this theme.
What at you a card for my program it is not important.
Simply  in the program I have put parameters of this card (8 and 16 bits , sample rate from 11025 to 96000 sps). If you have other card that may be it to best. At frequency 192000, 96000 sps and 16 bit programs will not work as I did not use such parameters. But I can change the program under your sound card. For this purpose what maximal sample rate is necessary to know for me at 8 bits and at 16 bits. It is possible to change it and on 24 bits. But it has not practical importance. The program works at nootbooks (desktop PC) with Windows XP.
Using of the microprocessor (PICs) does not possible for difficult program processing (digital) of a signal.

best wishes
wus47

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